Metabolism of 2-3H- and 4-14C-17alpha-ethynylestradiol 3-methyl ether (mestranol) by women.

The metabolism of 2-tritium- and 4-carbon-14-17alpha ethynylestradiol 3-methyl ether (mestranol) by women was investigated. A mixture of tritiated and carbon-14 mestranol was administered orally to 5 women and tritiated mestranol alone to 1 woman. Reactions involving position 2 were extensive as determined by liberation of tritium into body water (14-45% of the dose). Urinary metabolites (17alpha-ethynylestradiol, 2-hydroxy-17alpha-ethynylestradiol, 2-methoxy-17 alpha ethynylestradiol, 2-hydroxy-17alpha-ethynylestradiol 3-methyl ether and 16beta-hydroxy-17alpha-ethynylestradiol) were measured by addition of authentic steroids to both the "glucuronide" and pH1 fractions and reisolation by countercurrent distribution, derivative formation and thick layer chromatography. 2-methoxyestradiol accounted for less than .011% of the carbon 14 dose in the "glucuronide" fraction of 1 woman, which is consistent with the extent of deethynylation previously reported.